Eliminating uncertainty of thermal emittance measurement in solenoid scans due to rf and solenoid fields overlap

Abstract

The solenoid scan is one of the most common methods for the in-situ measurement of the thermal emittance of a photocathode in an rf photoinjector. The fringe field of the solenoid overlaps with the gun rf field in quite a number of photoinjectors, which makes accurate knowledge of the transfer matrix challenging, thus increases the measurement uncertainty of the thermal emittance. This paper summarizes two methods that have been used to solve the overlap issue and explains their deficiencies. Furthermore, we provide a new method to eliminate the measurement error due to the overlap issue in solenoid scans. The new method is systematically demonstrated using theoretical derivations, beam dynamics simulations, and experimental data based on the photoinjector configurations from three different groups, proving that the measurement error with the new method is very small and can be ignored in most of the photoinjector configurations.

References in corpus (10)

• Direct measurement of sub-10 fs relativistic electron beams with ultralow emittance
• Thermal emittance measurements of a cesium potassium antimonide photocathode
• An Engineering Guide To Photoinjectors
• Exact Cancellation of Emittance Due to Coupled Transverse Dynamics in Solenoids and RF Couplers
• OPAL a Versatile Tool for Charged Particle Accelerator Simulations
• Nano-machining, surface analysis and emittance measurements of a copper photocathode at SPARC_LAB
• Overestimation of thermal emittance in solenoid scans due to coupled transverse motion
• Experimental demonstration of the correction of coupled transverse dynamics aberration in an rf photoinjector
• Sources of Emittance in RF Photocathode Injectors: Intrinsic emittance, space charge forces due to non-uniformities, RF and solenoid effects
• Single shot cathode transverse momentum imaging in high brightness photoinjectors